InverseProperty with Database Migration doesn't work when property is protected or internal - entity-framework

Question

I have the following Entity Models
public class User
{
public virtual long Id{get; set;}
[InverseProperty("Users")]
public virtual ICollection<Tag> Tags { get; protected set; }
}
public class Tag
{
public virtual long Id{get; set;}
internal protected virtual ICollection<User> Users { get; set; }
}
This is pure simple many-to-many relation User & Tag
I'm using Data Migrations. When I execute the command Add-Migration or Update-Database
I get the following error "The InversePropertyAttribute on property 'Tags' on type 'Kigg.DomainObjects.Entities.User' is not valid. The property 'Users' is not a valid navigation property on the related type 'Kigg.DomainObjects.Entities.Tag'. Ensure that the property exists and is a valid reference or collection navigation property."
When I changed the access modifier of Users property in Tag to public it worked fine and the generation is what I want.
From my design point of view I want to hide the Tag.Users property and make it protected or internal to keep it for internal use as I don't want to expose it to public API.
Note: I'm not discussing the my design here. I'm asking if it's possible to do that while Tag.Users is protected or internal?

Answer 1

I don't know how to make it work with data annotations but with Fluent API you can apply and experiment with the trick from here: http://blog.cincura.net/232731-mapping-private-protected-properties-in-entity-framework-4-x-code-first/
For your model it would look like the following:
public class User
{
public virtual long Id{get; set;}
public virtual ICollection<Tag> Tags { get; protected set; }
}
public class Tag
{
public virtual long Id{get; set;}
internal protected virtual ICollection<User> Users { get; set; }
public class PropertyAccessors
{
public static readonly Expression<Func<Tag, ICollection<User>>> Users
= t => t.Users;
}
}
Mapping in FluentAPI:
modelBuilder.Entity<User>()
.HasMany(u => u.Tags)
.WithMany(Tag.PropertyAccessors.Users);
This works and creates the expected many-to-many relationship.
But I am not sure if you can do anything useful with that navigation property. The fact that you have the property protected and virtual lets me guess that you basically want lazy loading support inside of the entity class or derived classes.
The problem is that apparently (according to my tests at least) lazy loading doesn't work for anything else than a public property. The loaded tag is a proxy but the navigation collection is always null (unless the property is public).
Moreover, even eager and explicit loading don't work:
Outside of the Tag class:
// Eager loading
var tag = context.Tags.Include(Tag.PropertyAccessors.Users).First();
// Explicit loading
var tag2 = context.Tags.First();
context.Entry(tag2).Collection(Tag.PropertyAccessors.Users).Load();
Or inside of the Tag class (some method in Tag which gets the context passed):
public DoSomething(MyContext context)
{
// Eager loading
var tag = context.Tags.Include(t => t.Users).First();
// Explicit loading
context.Entry(this).Collection(t => t.Users).Load();
}
In all cases I get an exception that the property Users on entity Tag is not a valid navigation property. (The exception disappears as soon as I make the property public.)
I don't know if adding/removing/updating relationships would work. (I doubt.)
It looks that you can map a non-public navigation property with this approach to generate the expected database schema. But it seems that there is nothing useful you can do with it.

Answer 2

I don't know much about EF5 but you can use the attribute InternalsVisibleToAttribute to make internal members visible to a specific assembly.